Under Armour's global headquarters is located next to Baltimore's Inner Harbor. / Under Armour

by Gary Mihoces, USA TODAY Sports

by Gary Mihoces, USA TODAY Sports

The lawsuit is about a contested will. Actually, a contested, "I Will."

Under Armour has filed suit in federal court in Baltimore against sports apparel rival Nike, alleging Nike has infringed on Under Armour trademarks by using variants of the phrase "I Will" in promotional campaigns.

Under Armour's familiar slogan is "I will â?¦ protect this house.'' The Baltimore-based firm says in the suit filed Thursday that it is protecting its catchphrase.

"Defendant's use of I WILL infringes Under Armour's long-established trademark rights, dilutes the distinctiveness of Under Armour's famous mark, and constitutes unfair competition," the suit says.

The suit says Under Armour's right to the phrase goes back to as early as 1998 and that it has been featured in hundreds of products and on billboards, stadium signage, Internet ads and the company's homepage.

In an e-mail to USA TODAY Sports, Nike spokeswoman Mary Remuzzi said the company, which had just learned of the lawsuit, had no comment at this time.

This month, Under Armour launched a global marketing campaign called "I Will."

"Ten years ago Under Armour became a household name when the brand asked athletes everywhere to 'Protect this House.' The response in the iconic commercial, and throughout the years, has been the same: I WILL," Under Armour founder Kevin Plank said in a Feb. 12 news release.

The suit alleges Nike, based in Oregon, has infringed on that in multiple ways.

According to the suit, there are images of the Nike Facebook page with slogans such as "I will protect my home court" and "I will finish what I started."

The suit also says Nike's Facebook page and YouTube video page feature a video that includes images of athletes with such phrases as "I will sweat while they sleep" and "I will give the scout no other choice."

The suit alleges such usage is "likely to cause confusion, mistake, and deception as to the source or origin" and is "likely to falsely suggest a sponsorship, connection or association" with Under Armour.

Under Armour says it is guarding its phrase the same way Nike protects its "Just Do It" slogan.

"The I WILL trademark is one of the cornerstone symbols of our company and its products and services, and has been for many years," Under Armour said in a statement.

The suit, which seeks a trial by jury, asks for a permanent junction to stop Nike from using "I Will." It also asks for destruction of all Nike products that bear the phrase. It asks that Nike pay Under Armour "any and all profits arising from" such products. And it seeks treble damages "in an amount as yet determined."

Nike has annual sales of about $25 billion worldwide. Under Armour's suit said it had sales of $1.8 billion in 2012.